JP3551578B2 - Variable valve train for internal combustion engines - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a variable valve apparatus for an internal combustion engine that variably controls a lift amount and an opening / closing timing of an intake valve or an exhaust valve (hereinafter, both are generally referred to as intake and exhaust valves) of the internal combustion engine.
[0002]
[Prior art]
As this type of apparatus, for example, an apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 6-108810 is known. This device presses hydraulic oil along a cam lift by reciprocating a cam-side plunger with a camshaft, and hydraulically drives an intake / exhaust valve with the pressurized hydraulic oil. A hydraulic release valve for releasing pressurized hydraulic oil to the accumulator is provided in the hydraulic oil supply path. If the release valve is opened in the middle of the lift of the intake / exhaust valve, the pressure of the hydraulic oil decreases, so that the intake / exhaust valve switches to the seating operation from the middle of the lift by the urging force of the valve spring. That is, the lift amount of the intake / exhaust valve can be variably controlled by the opening timing of the release valve. In addition, the high-pressure hydraulic oil discharged through the hydraulic release valve is introduced into the accumulator, and is then returned to the hydraulic chamber from the accumulator when the cam lift decreases. The applied energy is added to the driving force of the cam, and the energy can be effectively used as a whole.
[0003]
Further, this device is provided with a hydraulic lost motion means in parallel with the accumulator. In this hydraulic lost motion means, a piston is urged by a spring in a direction to reduce the accumulator in the cylinder, and this accumulator is connected to the hydraulic chamber, and a back pressure chamber opposite to the accumulator is connected to the hydraulic chamber. It is connected to another accumulator via a pilot valve. When the pilot valve is closed, even if the hydraulic pressure rises due to the start of the cam lift, the operation of the piston is prevented. Therefore, the lift of the intake / exhaust valve is performed along the cam lift indicated by the dotted line in FIG. When the valve is opened, the piston moves at the same time as the start of the cam lift, and after a certain amount of hydraulic oil is absorbed in the accumulator, the lift of the intake and exhaust valves is started. That is, as shown by the solid line in FIG. 3, when the pilot valve is opened, the start of the lift of the intake / exhaust valve is delayed by θ.
[0004]
[Problems to be solved by the invention]
However, in such a conventional configuration, it is necessary to introduce hydraulic oil also to the back pressure chamber of the hydraulic lost motion means, and to provide an accumulator separately from the hydraulic lost motion for energy recovery, such as an oil passage. The configuration is complex and large. The hydraulic release valve also has a solenoid valve and a main valve body and occupies a large space, and together with the hydraulic lost motion means, the weight of the engine head becomes heavy, and noise and vibration are generated. Can cause problems.
[0005]
Further, when the pilot valve is opened, a certain amount of hydraulic oil is absorbed by the hydraulic lost motion means to delay the start of lift of the intake / exhaust valve, so that the lift start can be switched only in two ways. The valve opening time cannot be arbitrarily changed.
[0006]
An object of the present invention is to provide a lightweight and compact variable valve operating device for an internal combustion engine.
[0007]
[Means for Solving the Problems]
A variable valve apparatus for an internal combustion engine according to the present invention includes an intake valve or an exhaust valve constantly urged in a closing direction by a valve spring, a cam-side plunger driven by a camshaft and pressurizing hydraulic oil in a main hydraulic chamber. A valve-side plunger that receives the pressurized oil pressure in the valve-side hydraulic chamber and lifts the intake valve or the exhaust valve, and reduces the oil pressure in the main hydraulic chamber to the low-pressure side during the lift of the intake valve or the exhaust valve. A value obtained by dividing the biasing force of the valve spring at the time of the maximum lift of the intake valve or the exhaust valve by the pressure receiving area of the valve side plunger. A first accumulator that is set to be larger than the first accumulator, and valve means interposed between the main hydraulic chamber and the valve-side hydraulic chamber.
[0008]
When the valve means is closed, even if the hydraulic pressure in the main hydraulic chamber rises due to the start of the cam lift, the hydraulic oil is all absorbed by the first accumulator and the intake and exhaust valves are not lifted at all. Is opened, all the hydraulic oil in the first accumulator flows into the valve side hydraulic chamber, the intake / exhaust valve starts abrupt lift, and thereafter, the lift along the cam lift is performed. That is, by changing the valve opening timing of the valve means, the valve opening timing of the intake / exhaust valve changes.
[0009]
According to the second aspect of the present invention, the low-pressure-side hydraulic pressure releasing means includes a second accumulator in which an accumulator chamber is defined by a slidable plunger, and a pilot pressure passage connecting the accumulator chamber and the main hydraulic chamber. A pilot valve that is configured separately from the second accumulator, and that opens and closes the pilot pressure passage; and urges the plunger in a direction in which the accumulator chamber is reduced, and from the main hydraulic chamber via the pilot valve. An accumulator spring whose biasing force is set so that the accumulator is displaced by the introduced oil pressure, and a hydraulic pressure that opens the circuit with the plunger of the accumulator displaced and communicates the main hydraulic chamber and the accumulator chamber. And a release passage.
[0010]
When the pilot valve is opened during the lift of the intake / exhaust valve, the hydraulic pressure in the main hydraulic chamber is released to the second accumulator in a low pressure state, so that the intake / exhaust valve switches to the seating operation. The high-pressure hydraulic oil that has flowed into the accumulator chamber displaces the accumulator spring and is accumulated in the accumulator. Therefore, when the lift of the cam decreases, the hydraulic oil is pushed back from the accumulator chamber into the hydraulic chamber. Thereby, energy can be recovered. In a state where the piston of the accumulator is displaced, the hydraulic pressure release passage communicates with the accumulator chamber with a sufficiently large passage opening area and does not have a check valve in the passage, so that the hydraulic chamber and the accumulator chamber are The energy loss accompanying the reciprocation of the hydraulic oil between is small.
[0011]
According to the third aspect of the present invention, a first passage connecting the main hydraulic chamber and the valve-side hydraulic chamber via the valve means, and opening to a bottom surface of the valve-side hydraulic chamber; A second passage that directly connects to the valve-side hydraulic chamber and opens to the bottom peripheral surface of the valve-side hydraulic chamber; and a branch from the valve means of the first passage and the valve-side hydraulic chamber via an orifice. And a drain passage for cooling.
[0012]
At the start of the lift of the intake / exhaust valve, hydraulic oil is supplied from the first passage to the valve side hydraulic chamber, and the displacement of the valve side plunger is started. Is supplied, the opening of the valve means may be instantaneous. Further, the second passage is closed by the valve-side plunger immediately before the intake / exhaust valve is seated, and thereafter, the hydraulic oil in the valve-side hydraulic chamber is discharged through the orifice and the drain passage. Done.
[0013]
According to the fourth aspect of the present invention, a check valve is provided between the main hydraulic chamber and the valve means in the first passage so as to allow only the flow of hydraulic oil from the main hydraulic chamber to the valve means side.
[0014]
When hydraulic oil is returned from the valve side hydraulic chamber to the main hydraulic chamber, the first passage is closed by the check valve, and the hydraulic oil is discharged to the drain passage only through the orifice. As a result, a damping action always occurs when the intake / exhaust valve is seated, which makes it easy to control the closing timing of the valve means.
[0015]
In the invention according to claim 5, a plurality of the intake valves or the exhaust valves are arranged in the same cylinder, and one cam-side plunger is arranged in the same cylinder, so that the main hydraulic chamber and each valve-side hydraulic chamber are separated from each other. The valve means is interposed in each of the connecting passages.
[0016]
By shifting the valve opening timing of each of the valve means, a lift difference can be generated between a plurality of intake and exhaust valves in the same cylinder. An intake swirl is generated during rotation, the gas flow is activated, and deterioration of combustion at the time of low lift control of the intake valve can be prevented.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0018]
1 and 2 are cross-sectional views of a main part of an internal combustion engine showing a first embodiment of the present invention. Two intake valves 2 are slidably mounted on a cylinder head 1 and two Each is always urged in the closing direction by the valve spring 3. On the upper surface side of the cylinder head 1, a housing 4 of the lift control unit is arranged so as to overlap, and on the lower surface side of the housing 4, two cylinders 5 are mounted. A valve-side plunger 6 is slidably fitted in each of the cylinders 5. The tip ends of these valve-side plungers 6 abut the stem ends of the intake valves 2, and the plungers 6 are moved by hydraulic pressure to push and open the intake valves 2 respectively. Note that a tapered portion 60 is formed at the tip of the valve side plunger 6.
[0019]
A cylinder 7 is mounted on the upper surface side of the housing 4, and a cam-side plunger 8 is slidably disposed in the cylinder 7. The cam-side plunger 8 is urged upward by a spring 9 housed in the cylinder 7. The main hydraulic chamber 10 in the cylinder 7 communicates with the valve-side hydraulic chambers in the left and right cylinders 5 via first and second passages 11 and 12, respectively. Each of these passages 11 and 12 is branched into two on the way, and opens to the bottom surface and the bottom peripheral surface of the valve side hydraulic chamber. In the first passage 11, a pilot valve 13 as valve means is interposed between the main hydraulic chamber 10 and a branch point. Further, a drain passage 15 having an orifice 14 is connected to a branch point of the first passage 11, and the valve side hydraulic chamber is opened to the oil pan 42 via the drain passage 15. The tip of the drain passage 15 extends to the bottom of the oil pan 42 so that air is not sucked.
[0020]
That is, the cam-side plunger 8 is driven via the rocker arm 18 by the cam 17 of the camshaft 16 which rotates in synchronization with the crankshaft (not shown) of the internal combustion engine. By rotating, it reciprocates and pressurizes hydraulic oil in the main hydraulic chamber 10. Then, the pressurized hydraulic pressure is introduced into each cylinder 5 through the first and second passages 11 and 12, and each valve-side plunger 6 is pressed in the lift direction of the intake valve 2.
[0021]
In this embodiment, the pilot valve 13 is constituted by an ON / OFF-type solenoid valve that opens and closes depending on the presence or absence of energization. That is, as shown in FIG. 3, the pilot valve 13 has a needle-shaped valve body 19 slidably supported, and the valve body 19 is normally urged by a spring 20 in a valve closing direction. At the same time, a solenoid 21 is provided so as to urge the valve element 19 in the valve opening direction. In the pilot valve 13, the portion of the first passage 11 on the valve side hydraulic chamber side opens toward the side surface of the valve body 19, and the portion on the main hydraulic chamber 10 side opens toward the tip of the valve body 19. It is installed as follows.
[0022]
The valve body 19 receives a pressing force in the valve opening direction by the hydraulic pressure from the main hydraulic chamber 10, but is pressed in the seating direction by the urging force of the spring 20 to oppose the pressing force. The biasing force of the spring 20 is set to always exceed the pressing force in the lift direction by the hydraulic pressure from the main hydraulic chamber 10, and the valve body 19 is securely held in the seated state when the power supply to the solenoid 21 is stopped. . When the solenoid 21 is energized, the valve body 19 is attracted in the lift direction by the magnetic force, and the valve body 19 is lifted by exceeding the urging force of the spring 20.
[0023]
Further, a first accumulator 22 is connected to the main hydraulic chamber 10 in order to variably control the valve opening timing of the intake valve 2 according to operating conditions and the like. The accumulator 22 has a plunger 24 slidably disposed in a cylinder 23, and the plunger 24 is urged by an accumulator spring 25 in a direction in which the accumulator chamber is reduced. The back pressure chamber 26 in which the accumulator spring 25 is housed is opened to the atmosphere via a communication hole 27. The accumulator 22 determines the cracking pressure (the value obtained by dividing the urging force of the accumulator spring 25 when the plunger 24 is not displaced by the pressure receiving area of the plunger 24) by the urging force of the valve spring 3 during the maximum lift of the intake valve 2. It is set to be larger than a value obtained by dividing the pressure receiving area of the side plunger 6.
[0024]
Hydraulic oil is supplied to the main hydraulic chamber 10 from a hydraulic oil supply passage 29 via a check valve 28. The hydraulic oil supply passage 29 is connected to a discharge side of an oil pump (not shown). Communicating. The hydraulic oil supply system is integrated with the engine lubrication system. The engine lubrication oil is used as the hydraulic oil, and the lubrication oil pump mechanically driven by the engine output is used as it is.
[0025]
The housing 4 has a second accumulator 30 functioning as a release valve in order to variably control the lift amount and the valve closing timing of the intake valve 2 according to operating conditions and the like. A pilot pressure is applied to the accumulator 30. A supply pilot valve 31 is provided. The second accumulator 30 has a plunger 33 slidably disposed in a cylinder 32, and the plunger 33 defines an accumulator chamber 34. The plunger 33 is urged by an accumulator spring 35 in a direction in which the accumulator chamber 34 contracts. The back pressure chamber 36 in which the accumulator spring 35 is housed is opened to the atmosphere via a communication hole 37.
[0026]
The hydraulic pressure release passage 38 is connected to the second accumulator 30 from the main hydraulic chamber 10. The distal end of the hydraulic pressure release passage 38 is open toward the outer peripheral surface of the plunger 33, and is closed by the plunger 33 when the plunger 33 is not displaced. When the plunger 33 is displaced, the accumulator chamber 34 It is designed to communicate. The plunger 33 has a tapered portion 33 a on the accumulator chamber 34 side, and the biasing force of the accumulator spring 35 causes the tapered portion 33 a to come into pressure contact with the tapered surface of the cylinder 32, so that the closing seal of the hydraulic release passage 38 is closed. Has been done.
[0027]
A drain passage 40 is connected to the accumulator chamber 34 via an orifice 39, and the accumulator chamber 34 is opened to the oil pan 41 via the drain passage 40. The diameter of the orifice 39 is set to a value as small as possible so that the hydraulic pressure in the accumulator chamber 34 does not become the cracking pressure of the plunger 33 even if the high-pressure hydraulic oil leaks into the accumulator chamber 34 when the plunger 33 is not displaced. ing. Further, the tip of the drain passage 40 extends to the bottom of the oil pan 41 so that air is not sucked. Even if hydraulic oil leaks somewhat from the drain passage 40 through the contact surface between the plunger 33 and the cylinder 32, for example, from the hydraulic release passage 38, the inside of the accumulator chamber 34 is reliably maintained at a low pressure state.
[0028]
On the other hand, the pilot valve 31 is also constituted by an ON / OFF type solenoid valve that opens and closes depending on the presence or absence of energization, similarly to the pilot valve 31 installed in the first passage 11. That is, the pilot valve 31 has a needle-shaped valve body 43 slidably supported, and the valve body 43 is constantly urged by a spring in the valve closing direction, and the valve body 43 is urged in the valve opening direction. A solenoid 44 is provided so as to urge 43. The pilot valve 31 opens and closes a pilot pressure passage 45 connecting the main hydraulic chamber 10 and the accumulator chamber 43. In particular, the main hydraulic chamber 10 side portion of the pilot pressure passage 45 is opened toward the side surface of the valve body 43 so that the high hydraulic pressure from the main hydraulic chamber 10 does not act on the valve body 43 in the valve opening direction. The portion on the accumulator chamber 34 side is open toward the tip of the valve body 43. Therefore, even if a high surge pressure is generated in the main hydraulic chamber 10 when the cam lift rises, the pilot valve 31 does not open due to the influence.
[0029]
The valve element 43 receives a pressing force in the valve opening direction by the hydraulic pressure in the accumulator chamber 34, and is pressed in the seating direction by the urging force of the spring 44 to oppose the pressing force. The urging force of this spring is set so as to always exceed the pressing force of the accumulator chamber 34 in the lift direction by the hydraulic pressure, and the valve body 43 is securely held in the seated state when the solenoid 44 stops energizing. When the solenoid 44 is energized, the valve element 43 is attracted in the lift direction by the magnetic force, and the valve element 43 is lifted by exceeding the urging force of the spring. That is, in this embodiment, the second accumulator 30, the hydraulic release passage 38, and the pilot pressure passage 45 constitute a low-pressure hydraulic release unit.
[0030]
In this embodiment, one set of variable valve devices is installed on the intake valve side of each cylinder. The two pilot valves 13 and 31 are controlled to open and close by a controller (not shown).
[0031]
Next, the operation of the above embodiment will be described. In this device, when the opening timing of the intake valve 2 is changed, the pilot valve 13 is in a closed state in advance when the lift of the cam 17 is started. When the cam-side plunger 8 is pressed by the lift of the cam 17, the hydraulic pressure in the main hydraulic chamber 10 rises and exceeds the cracking pressure of the first accumulator 22, so that the plunger 24 of the accumulator 22 is displaced. The hydraulic pressure in the hydraulic chamber 10 is released here. Here, when the pilot valve 13 is opened, all the hydraulic oil in the first accumulator 22 flows into the valve-side hydraulic chamber, the valve-side plunger 6 is pushed down, and the lift of the intake valve 2 is started. Thereafter, the lift of the intake valve 2 is performed along the cam lift. That is, by changing the valve opening timing of the pilot valve 13, the valve opening timing of the intake / exhaust valve 2 changes. FIG. 7 shows the lift characteristics of this device. When the pilot valve 13 is opened, all the hydraulic oil in the first accumulator 22 flows into the valve-side hydraulic chamber. There is no reduction in the lift amount. If the pilot valve 13 is left open from the beginning, the pressurized hydraulic oil all flows into the valve-side hydraulic chamber having a low cranking pressure, and the lift of the intake valve 2 is performed along the cam lift. .
[0032]
By the way, when the solenoid 44 of the pilot valve 31 is energized during the lift of the intake valve 2, the pilot valve 31 opens, and the hydraulic pressure in the main hydraulic chamber 10 passes through the pilot pressure passage 45 and the accumulator of the second accumulator 30. It is introduced into the chamber 34 as pilot pressure. In a state where the pilot pressure is introduced, the spring force and the pressure receiving area are set so that the pressing force by the oil pressure in the accumulator chamber 34 exceeds the urging force of the accumulator spring 35, so that the plunger 33 pushes the accumulator spring 35. Displaced upward while shrinking. Thereby, the hydraulic pressure release passage 38 is opened. That is, the leading end of the hydraulic pressure release passage 38 and the accumulator chamber 34 communicate with each other, and the hydraulic pressure in the main hydraulic chamber 10 is released to the accumulator chamber 34 in the low pressure state. Therefore, the intake valve 2 switches to a seating operation during the lift. Here, since the plunger 33 is relatively large in order to secure the capacity required for the accumulator 30, the passage opening area of the hydraulic release passage 38 when the plunger 33 is displaced can be sufficiently large. . Therefore, the energy loss when the hydraulic oil moves from the main hydraulic chamber 10 to the accumulator chamber 34 is very small.
[0033]
Thereafter, when the lift of the cam 17 gradually decreases, the hydraulic oil stored in the accumulator chamber 34 is pushed back into the main hydraulic chamber 10 through the hydraulic release passage 38. This hydraulic energy contributes to the rotation of the camshaft 16, whereby the energy is recovered. As described above, when hydraulic oil returns from the accumulator chamber 34 of the second accumulator 30 to the main hydraulic chamber 10, energy loss is extremely small because the check valve is not interposed in the path.
[0034]
By the way, since the valve-side hydraulic chamber communicates with the main hydraulic chamber 10 via the first and second passages 11 and 12, hydraulic fluid is supplied from the first passage 11 at the start of the cam lift. When the plunger 6 is displaced to some extent, the supply of the hydraulic oil is also performed from the second passage 12. Therefore, it is only necessary to instantaneously open the pilot valve 13 and supply the pilot pressure to the valve side hydraulic chamber. Immediately before the intake valve 2 is seated, the opening of the second passage 12 to the cylinder 5 is closed by the valve-side plunger 6 and the pilot valve 13 is already closed. The working oil in the room is discharged to the oil pan 42 through the orifice 14 and the drain passage 15, and the seating of the intake valve 2 is performed gently. At this time, the opening of the second passage 12 is gradually narrowed by the tapered portion 60 of the valve-side plunger 6, and functions as a variable orifice that gradually decelerates the valve-side plunger 6.
[0035]
Further, even if the hydraulic oil slightly leaks from the hydraulic release passage 38 to the accumulator chamber 34 through the contact surface with the cylinder 32 in a state where the plunger 33 of the second accumulator 30 is not displaced, for example, the leaked hydraulic oil remains in the orifice. 39, the oil is discharged to the oil pan 41 through the drain passage 40, so that the inside of the accumulator chamber 34 is reliably maintained at a low pressure state. That is, there is no fear that the plunger 33 of the accumulator 30 malfunctions due to leakage of the hydraulic oil into the accumulator chamber 34.
[0036]
As described above, according to the above-described embodiment, the lift of the intake valve 2 rises earlier than the conventional one, and even if the valve opening timing is delayed, the lift amount does not decrease at all. Therefore, pump loss of the engine is reduced, and fuel consumption is reduced. improves.
[0037]
Further, when the hydraulic oil reciprocates between the main hydraulic chamber 10 and the accumulator chamber 34 of the second accumulator 30, the energy loss can be extremely reduced, and the fuel consumption rate of the internal combustion engine can be improved accordingly. Further, the pilot valve 31 is configured separately from the accumulator 30 and only opens and closes the pilot pressure passage 45 having a relatively small passage area, so that the response does not deteriorate.
[0038]
4 and 5 show a second embodiment in which the opening timings of the left and right intake valves 2 can be changed separately.
[0039]
In this embodiment, a pilot valve 50 is provided in each of the branch portions 11a and 11b of the first passage 11, and a drain passage 52 having an orifice 51 is connected to the bottom of the left and right cylinders 5a and 5b. The hydraulic oil in 5a and 5b is released to oil pans 53a and 53b, respectively. Other points are basically the same as those of the first embodiment.
[0040]
In this case, a lift difference can be generated between the left and right intake valves 2a, 2b by shifting the opening timing of the left and right pilot valves 50a, 50b. Therefore, intake swirl can be generated when the engine is running at a low speed, the gas flow is activated, and deterioration of combustion during low lift control of the intake valve can be prevented.
[0041]
FIG. 6 shows a third embodiment in which a check valve 54 is provided in series with the pilot valve 13.
[0042]
In this embodiment, a check valve 54 is provided between the pilot valve 13 and the main hydraulic chamber 10 in the first passage 11 to allow the flow of hydraulic oil from the main hydraulic chamber 10 to the pilot valve 13 side. Other points are basically the same as those of the first embodiment.
[0043]
That is, in the above-described embodiment of FIG. 1, the closing operation of the pilot valve 13 needs to be performed in a very short time, but if the check valve 54 is provided in this manner, the operation of Since the oil is confined in the first passage 11 and spontaneously causes a damping action, the valve closing timing of the pilot valve 13 is easily controlled. Therefore, the pilot valve 13 may be closed when the lift of the cam 17 is completed.
[0044]
The two pilot valves 13 and 31 need only be able to apply a pilot pressure to the first and second accumulators 22 and 30 in a pulsed manner, and are limited to the electromagnetic type as shown in each of the above embodiments. It is not done.
[0045]
【The invention's effect】
As is clear from the above description, in the variable valve apparatus for an internal combustion engine according to claim 1, it is not necessary to introduce hydraulic oil into the back pressure chamber of the first accumulator, and the accumulator is separately provided for energy recovery. Since there is no need to provide this, not only the oil passage configuration is simplified, but also the low-pressure-side hydraulic release means can be simply composed of an accumulator, pilot valve, etc., so that the weight of the engine head is reduced and noise and vibration are generated. Can also be prevented.
[0046]
Further, when the valve means is opened, the hydraulic oil flows from the first accumulator into the valve side hydraulic chamber to start the lift of the intake / exhaust valve, so that the opening timing of the intake / exhaust valve can be arbitrarily changed. Further, even if the intake valve lifts quickly and the valve opening timing is delayed, the lift amount does not decrease at all, so that pump loss of the engine is reduced and fuel efficiency can be improved.
[0047]
Further, when the low-pressure side hydraulic pressure releasing means is provided as in claim 2, the hydraulic pressure releasing passage communicates with the accumulator chamber with a sufficiently large passage opening area when the piston of the second accumulator is displaced, and Since no check valve is provided in the passage, the energy loss accompanying the reciprocation of the hydraulic oil between the hydraulic chamber and the accumulator chamber can be reduced.
[0048]
According to the third aspect, the second passage is closed by the valve-side plunger immediately before the intake / exhaust valve is seated, and thereafter, the hydraulic oil in the valve-side hydraulic chamber is discharged through the orifice and the drain passage. Therefore, the seating of the intake and exhaust valves is performed gently.
[0049]
Further, when the check valve is provided as described above, the hydraulic oil is confined in the first passage immediately before the intake valve is seated and a damping action occurs, so that the valve closing timing control of the pilot valve is facilitated, The control circuit can be configured at low cost.
[0050]
In addition, according to the structure of the fifth aspect, by shifting the valve opening timing of the valve means, a lift difference can be generated between a plurality of intake and exhaust valves in the same cylinder. Therefore, when this variable valve device is applied to the intake valve side, the intake swirl can be strengthened when the engine is running at a low speed, the gas flow is activated, and the deterioration of combustion during low lift control of the intake valve can be prevented.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a variable valve apparatus according to the present invention.
FIG. 2 is a diagram showing a first embodiment of the variable valve operating device, and is a cross-sectional view taken along line AA of FIG.
FIG. 3 is an enlarged view showing the pilot valve of FIG. 1;
FIG. 4 is a sectional view showing a second embodiment corresponding to FIG. 1;
FIG. 5 is a view showing a second embodiment corresponding to FIG. 2;
FIG. 6 is a view showing a third embodiment corresponding to FIG. 1;
FIG. 7 is a view showing a lift characteristic of the present invention.
FIG. 8 is a diagram showing a lift characteristic of a conventional example.
[Explanation of symbols]
2. Intake valve
3. Valve spring
6… Plunger on valve side
8… Cam side plunger
10 ... Main hydraulic chamber
13 ... Pilot valve
22 ... First accumulator
30 second accumulator
31 ... Pilot valve
38 ... Hydraulic release passage
45 ... Pilot pressure passage

Claims (5)

An intake valve or an exhaust valve constantly urged in the closing direction by a valve spring,
A cam-side plunger driven by a camshaft and pressurizing hydraulic oil in a main hydraulic chamber;
A valve-side plunger that receives the pressurized hydraulic pressure in the valve-side hydraulic chamber and lifts the intake valve or the exhaust valve;
Low-pressure side hydraulic pressure release means for releasing the hydraulic pressure in the main hydraulic chamber to the low pressure side during the lift of the intake valve or the exhaust valve,
A first hydraulic pressure chamber connected to the main hydraulic chamber, the cracking pressure of which is set to be larger than a value obtained by dividing the urging force of the valve spring at the time of maximum lift of the intake valve or the exhaust valve by the pressure receiving area of the valve side plunger; An accumulator,
Valve means interposed between the main hydraulic chamber and the valve-side hydraulic chamber,
A variable valve train for an internal combustion engine comprising: The low-pressure-side hydraulic release means includes a second accumulator having a slidable plunger defining an accumulator chamber, a pilot pressure passage connecting the accumulator chamber to the main hydraulic chamber, and a second accumulator. And a pilot valve configured to open and close the pilot pressure passage, and a bias valve for urging the plunger in a direction in which the accumulator chamber is reduced, and a hydraulic pressure introduced from a main hydraulic chamber through the pilot valve. , The accumulator spring having its urging force set therein, and a hydraulic pressure release passage that opens the circuit with the plunger of the accumulator displaced and communicates the main hydraulic chamber and the accumulator chamber. The variable valve apparatus for an internal combustion engine according to claim 1, wherein: The main hydraulic chamber and the valve-side hydraulic chamber are connected via the valve means, and the first passage opening at the bottom of the valve-side hydraulic chamber is directly connected to the main hydraulic chamber and the valve-side hydraulic chamber. A second passage opening in the bottom peripheral surface of the valve-side hydraulic chamber; and a drain passage branched from the valve means of the first passage and the valve-side hydraulic chamber via an orifice. 3. The variable valve train for an internal combustion engine according to claim 1, wherein 4. The check valve according to claim 3, wherein a check valve is provided between the main hydraulic chamber and the valve means in the first passage so as to allow only the flow of hydraulic oil from the main hydraulic chamber to the valve means side. Variable valve train for internal combustion engines. A plurality of the intake valves or exhaust valves are provided in the same cylinder, and one cam-side plunger is provided in the same cylinder. 4. The variable valve train for an internal combustion engine according to claim 1, wherein a valve means is interposed.

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